Our laboratory is interested in purifying and characterizing intracellular compartments containing pathogenic microorganisms. Experiments were completed on the immunochemical characterization of neutrophil phagosomes containing Salmonella typhimurium. Our results show that cell surface phagocytic receptors and azurophil granule components are indiscriminately incorporated into phagosomes regardless of the ligand on S. typhimurium. In contrast, specific granule constituents are 4-5 fold more prominent in phagosomes containing IgG coated Salmonella than in phagosomes containing C3 coated Salmonella. Experiments were completed on the characterization of phagosomes in J774 cells containing Trypanosoma cruzi. Using both intracellular iodination and immunofluorescence, we showed that non-infective epimastigotes are internalized into vacuoles which contain the complement receptor CR3, whereas infective metacyclic trypomastigotes reside in CR3 negative vacuoles. Both compartments contain lysosome-specific glycoproteins, indicating that the parasitophorous vacuole has fused with lysosomes. Experiments were completed on characterization of parasitophorous vacuoles in Chinese Hamster Ovary (CHO) Cells containing Toxoplasma gondii. Native parasites entering CHO cells reside in compartments which neither acidify nor fuse with lysosomes or endosomes. Antibody coated or heat killed tachyzoites entering CHO cells transfected with the murine FcRII receptor reside in compartments which acidify and are fusigenic. These results illustrate three different forms of selectivity in incorporation or exclusion of membrane receptors and/or granule constituents into phagosomes.